In the course of my life as a documentary maker, I’ve been shot at, spat at, and abused. I’ve borne witness to some of the worst excesses in human behaviour, but an investigation I recently conducted for Channel 4’s Dispatches still held the power to shock.

For the last four months I have been examining the incidence of gang rape in Britain, after the widespread reporting of two such brutal attacks on women first brought this issue to the attention of the public.

I must confess to having a very personal reason for wanting to tackle this thorny subject. Back in 1999 I witnessed a gang rape in my country of birth, Sierra Leone. It was in the midst of the civil war and I was forced to watch a group of rebel soldiers taking it in turns to rape a young girl in front of an open-air audience of cheering men.

It was a flagrant and violent display and the images have stayed with me, but they are images I have always associated with civil war, not with the lives of Britain’s inner-city teenagers And yet in the course of my Dispatches investigation I have discovered that gang rape is becoming part of the fabric of life for some young people living in our cities. But it’s not gang rape as you might imagine – it’s not, in most cases, the seizing of girls off the streets by total strangers. It’s happening in homes and at parties between young people who are known to each other, who run in the same crowds. And what’s most disturbing to me is that it’s often just the result of a group of boys deciding to force sex on an unwitting girl, who doesn’t realise that the invitation to someone’s house to watch DVDs or to hang out in the local park is a set up for gang rape. It can happen because a group of boys is attracted to a particular girl or just because she has annoyed one of them.

In the course of my conversations with inner-city teenagers I felt that I had heard enough to convince me that what we’re dealing with here is a disturbing development in criminal behaviour, so with the help of the Dispatches team, I set out to discover, statistically, what the true nature and extent of this largely unrecognised problem is.

I say largely unrecognised because gang rape is not actually on the statute books as a separate criminal offence. Anyone charged with participating in such acts has to be tried in court for their individual offence. This means that there are no official statistics nationally and no true grasp as to the scale of the problem.

So as a first port of call Dispatches contacted the Crown Prosecution Service and the Association of Chief Police Officers to see if they held any figures. They didn’t. We then approached all 50 police forces in Britain, but many did not respond or said they do not have such information.

Fortunately for us, the Metropolitan Police do keep a record of sorts. They told us that in the last year alone, a total of 108 people reported gang rapes, which they define as a rape involving ‘three or more perpetrators’. Using this definition, we then spent the next four months trying to track down as much information as we could about as many cases as we could, verifying our information with the Crown Courts, Court Reporters and barristers. In the absence of comprehensive records, this proved to be a painstaking exercise.

We looked at offences involving perpetrators aged 25 and under, and managed to track down 29 cases in which a total of 92 young people were convicted of involvement in gang rape. Of those convicted, 66 of them were black or mixed race, 13 were white and the remainder were from other countries including Afghanistan, Iraq and Libya. Of the cases we found, two thirds of gang rapes occurred in London. We do not know if these were the only cases – they are simply the ones we could find.

On the face of it, these figures may appear small, but they are nevertheless statistically significant when you consider that nearly three quarters of those convicted were black. Why the incidence should be higher amongst young black men I do not know, but the stats speak for themselves, and on the ground youth workers and community leaders confirmed our conclusions. Sheldon Thomas, a Brixton youth worker, acknowledges that there are a disproportionate number of young black boys involved in gang rape, and it’s something that’s of real concern to him, ‘because we’ve got a situation in our community that needs to be addressed. And I don’t believe that we are addressing it’.

But whilst I would agree that we need to address the disproportionate incidence within the black community, I think it would be wrong to label this as a black issue. What we need is for people from across all communities and public sectors to engage with this issue, and colour must not get in the way of that.

It is precisely a lack of engagement between parents and children that has, in my view, created this problem in the first place. The kids I came across who slouch on their parents’ sofa watching TV that are not the same young people who congregate in the estates, streets and parks of urban Britain. These teenagers are leading double lives – a fact that became clear to me in the course of my investigation. For a few weeks I briefly inhabited a world I can barely comprehend – a world in which loyalty and respect take on a twisted and violent meaning and where rape is described by some young men as the tool ‘the police can’t stop and search you for’.

In the course of my research I have been shocked to hear victims and witnesses to gang rape talk about the incidence of this crime as if it were just a fact of urban life. Girls are passed around groups of boys. Sometimes these girls initially consent because they want to be popular, but the incident then turns nasty. Sometimes a girl unwittingly walks into a trap, innocently visiting someone’s house to listen to music or watch a film and then discovering that a group of boys are laying in wait. Occasionally the gang rape is used to punish a girl for talking out of turn.

One girl I spoke to vividly described how, at a party, she ‘walked into the wrong room and there was just loads of boys and the girl’s tights were ripped up, like, she was bleeding as well because I think she was a virgin and they were like just taking turns on her basically and she was like crying and I didn’t get involved yeah because I thought if I get involved they’re gonna turn on me’. A teenage rape victim likened her attack to being ‘pulled and pushed around like a rag doll’, while another 14-year-old girl described her ordeal when she was gang raped by a total of nine boys who told her that she was not the only girl they’d done it to and that she was ‘not going to be the one to grass them up either’. In fact, she did. All nine boys were subsequently convicted of raping her, with the youngest perpetrator being just 12 years old.

I’ve also had equally shocking conversations with young men about their attitudes to girls and to sex. To some that I spoke to, setting girls up to have sex or perform sexual acts on a number of boys, coercing and sometimes forcing them to do so in the process – these things are not wrong in their eyes and they’re not rape either, they’re just what these guys do…

Passing girls round to perform oral sex is a common practise that these boys call a ‘line up’.

In their eyes some girls are just asking for it.

‘You shouldn’t be too hasty to go and meet boys. If she wants to go and meet a bag of boys then she’s probably a jezzie (slut) and if she’s going to a house it’s over, she’s going to get beaten’.

And God help the girl who passes on an STD to such a boy because he’s likely to ‘batter’ her.

As the father of five, I’ll admit that I’m struggling to know how to parent them in the light of what I’ve learned – how to protect them. So I’ve done the only thing I can, and put my kids under curfew until I work out how to give them their freedom but keep them safe.

I settled in Britain in the early 1990s and chose to raise my children here. I never thought that one day I’d be making a film about British life that reflects the worst excesses of the civil war I fled.

I don’t want this film to represent any kind of legacy for my kids. I want gang rape to be an anomaly in crime trends, but I fear it’s not a blip. Frighteningly, those on the ground trying to tackle youth crime say that the cases I have looked at are just a sign of things to come. Reverend Joyce Daley, from the Black Parents Forum says that gang rape is not a rare or one off phenomenon, it is happening on a regular basis and if we don’t put a stop to it now, ‘it could actually explode on our very streets’.

But how we put a stop to it is difficult to answer. In the experience of Brixton-based youth worker, Sheldon Thomas, ‘we’ve got a generation that look at sex as if it’s nothing and treat disrespecting women as if it’s nothing. These guys are like 13 and 14 and 15 and their actual attitudes towards young girls, towards sex is mind blowing because it’s actually leaving you with where’s their morals where’s their values?’

I don’t know how we reverse these attitudes or how we help young boys and girls to redefine the notion of respect for themselves and for others. And I don’t know how, as parents, we re-connect with our children. I do know, though, that dialogue has to lead the way.

And as a first step I hope that my Dispatches findings bring this issue sharply into focus so that the debate can begin.